Television antenna system



Aug. 28, 1951 L. H. FINNEBURGH, JR

TELEVISION ANTENNA SYSTEM Filed Sept. 16, 1950 2 Sheets-Sheet 1 M .5 n 2m A Y. B

23, 1951 L. H. FINNEBURGH, JR 2,566,287

' TELEVISION ANTENNA SYSTEM Filed Sept. 16, 1950 2 Sheets-Sheet 2 514 C/\ /CZ A S C C 0 s w T T z y 51 I Z INVENTOR F1 11 BY ATTORNEYS Lewis liFinneburgh Jr.

Patented Aug. 28, 1951 UNITED STATES PATENT OFFICE TELEVISION ANTENNA SYSTEM Lewis H. Finneburgh, J r., Cleveland Heights, Ohio Application September 16, 1950, Serial No. 185,197

This invention relates to antenna systems and particularly to high gain, directive antenna systems for television transmission and reception.

The principal object of the invention is to provide a high-gain antenna system that will be responsive with almost uniform, maximum gain over a wide range of frequencies covering at least the range of the present high or low television bands, and that will be responsive with good performance over both the present high and low bands.

Another object of the invention is to provide an antenna system having the foregoing performance characteristics and having an aerial structure suitable for mounting on a single, rotatable mast.

A further object of the invention is to provide an aerial structure that may be shipped in a completely assembled, collapsed condition, and that may be quickly extended in an accordionlike ,manner at the place of installation for mountin on a mast to provide an antenna system of the character described.

Still another object of the invention is to accomplish the foregoing objectives while making the greatest possible structural use of electrically functional members, thereby keeping the amount of material in the aerial structure to a minimum consistent with the results to be achieved.

structurally, the aerial resembles two vertically stacked sets of three half wave collinear units with quarter wave, phase reversing stubs, one of the two sets being inverted with respect to the other to bring their stubs back to back, both sets being supported in laterally spaced parallel relationship with respect to a pair of similarly stacked reflectors, and the whole being mounted on a vertical mast. Electrically, however, the antenna system differs radically from such an assembly, and, in addition, possesses certain novel structural characteristics not immediately apparent from an inspection of the complete assembly.

As used above, and throughout the remainder of this application, including the claims, the term collinear units is employed to designate a plurality of straight conductors disposed in longitudinal alignment along a substantially straight line; and the term separated collinear units is employed to designate a set of collinear units that are physically separated from each other, as by means of an intervening insulator or by merely being physically spaced apart in space to interrupt the linear continuity of the set of units as a whole.

Claims. (01. 250--33.53)

' be more fully The principal electrical feature of the invention resides in the discovery that remarkable broad banding effects are achieved when such a vertically stacked pair of back to back sets of collinear units have the adjacent ends of their A oppositely disposed stubs electrically connected,

as by closing their ends with a common conductor.

The principal structural feature of the invention resides in the employment of pivotal connections at each corner of each individual stub so that each pair of oppositely disposed rectangular stubs having a common side may be 001 lapsed, as folding parallelograms, to permit the two sets of collinear units and reflectors to be brought together for packaging, pulled apart again at the place of installation, and quickly converted into a relatively rigid structure.

A third feature of the invention resides in the use of the upper and lower cross arms as elec trically functioning units, serving the purpose of reflectors, as well as supports for the upper and lower sets of collinear units, respectively.

These special features of the invention and various other objects and advantages thereof will understood from the following detailed, description of an illustrative embodiment of the invention, taken in conjunction with the accompanying drawings, in which;

Figure 1 is a perspective view looking upwardly at an antenna embodying the invention;

Fig. 2 is an end elevation on an enlarged scale of the aerial structure and mast of the antenna shown in Fig. 1, the view being taken as indicated by the line 2--2 of Fig. 1;

Fig. 3 is a fragmentary plan view on a further enlarged scale of the aerial structure and mast of Fig. l, the view being taken as indicated by the line 33 of Fig. 1.

Fig. 4 is a fragmentary vertical section through the aerial structure and mast of Fig. 1, the View being on the same scale as Fig. 3 and taken as indicated by the lines 4-4 in Figs. 1 and 3;

Fig. 5 is another fragmentary plan view showing a detail of the aerial of Fig. 1 on the scale of Figs. 3 and 4 Fig. 6 is a front elevation of the Fig. 5;

Fig. 7 is another fragmentary, vertical section showing a detail of the aerial of Fig. 1 on the same scale as Figs. 3 to 5.

Fig. 8 is a fragmentary elevation of the aerial of Fig. l in a partially collapsed condition;

Fig. 9 is a diagrammatic elevation of the principal aerial elements of Fig. 1 in a partially collapsed condition, the relationship of the elements detail of when fully extended being indicated in dot-anddash lines;

Fig. is a diagrammatic elevation of a pair of conventional aerial units arranged in stacked relation with one inverted with respect to the other, this illustration being given for comparative purposes.

Fig. 11 is a similar, diagrammatic elevation showing the changes from Fig. 10 that were most significant in bringing about the improved electrical operation achieved by the invention.

Referring principally to Fig. l and to the details shown in Figs. 2 to 7, the aerial structure of the antenna system illustrated is carried by a single vertical mast l2, that may take the form of a rigid, hollow, metal tube mounted in any desired manner (not shown) for rotation about its vertical axis.

A top cross arm I3 and a lower cross arm 14 are mounted at their centers adjacent the top of the mast and extend horizontally in vertically spaced-apart parallel relation. The cross arms l3 and I4 may also take the form of hollow, metal tubes, preferably being made of a light metal and smaller in diameter than the mast I2, but large enough in diameter to remain substantially rigid while carrying the remainder of the aerial structure.

The cross arms l3 and M are rigidly secured to the mast l2 by suitable brackets, such as the one illustrated in detail in Figs. 3 and 4. In this illustrative embodiment, the bracket comprises a short, channel shaped member I6 extending horizontally and having notches I! in its flanges for receiving the mast l2. The web or back of the channel shaped member I6 is formed with a longitudinally extending groove I8 therein to receive the cross arm H3 (or M). The channel shaped member is secured against the mast and the cross arm is secured against the channel shaped member by a U-bolt I 9 that straddles the mast with its legs extending through aligned pairs of apertures in the channel shaped member and in the cross arm, and by a cooperating pair of nuts 2! and washers 22. As will be apparent, the nuts 2| may readily be tightened to hold the described assembly in position.

The embodiment of the invention illustrated herein includes a set of three separated collinear units of equal, selected resonant lengths mounted on each cross arm, all being more fully described hereinafter. To mount the two sets of collinear units on their respective cally through the cross arms with support flared out at drawal.

an end of each 26 to prevent its withand for supporting the center unit at a break in the center thereof. The two outermost supports 23 on each cross arm both carry suitable bracing insulators 3| thereon for giving additional support to the end collinear units of each set.

The spacing insulators 29 may conveniently be rectangular in form with holes drilled therethrough at their ends to receive machine screws 32, to which the adjacent looped ends of collinear units are secured by nuts 33. Each spacing insulator 29 may be mounted on its support 23 by another machine screw 34, which may be threaded into a nut 36 jammed into the end of the support 23.

The bracing insulators 3| are preferably in the form of square blocks of sufficient thickness for holes 31 .to be drilled edgewise therethrough to receive the end collinear units. Each bracing insulator may be mounted on its support 23 by means of a machine screw 38 threaded into a nut 39 jammed into the end of the support 23.

The two sets of collinear units respectively associated with the upper and lower cross arms I 3 and M are identical, and a description of one is equally applicable to the other; Referring to either set, the center unit 4| is broken in the middle, as noted above, to provide two separated conductor parts Ma and M b having their adjacent ends connected to a spacing insulator 29, as described above. The outer units 42 and 43 are unbroken conductors that are collinear with the center unit and are physically and electrically spaced therefrom at opposite ends thereof by additional spacing insulators 29, as described above.

The physical lengths of the units 4i 42, and 43 are empirically selected in accordance with well known principles to be of substantially equal resonant lengths of wave length each, or any whole multiple thereof, the wave length upon which their dimensions are based being a selected one in about the center of the range of Wave lengths to which maximum response of the connected circuit is desired. Thus, the upper and lower sets of collinear units per se are conventional.

As will be apparent from the foregoing description of the manner in which each set of collinear units is mounted with respect to its cross arm, each cross arm is insulated from the collinear units carried thereby and serves both as a structural support and as a reflector therefor. This arrangement elTects a considerable economy of material by eliminating the electrically non functional cross arm usually disposed between the collinear units and the reflector.

In an effort to find means for improving the gain and for broadening the band response of two vertically stacked sets of collinear units of the character described above (each unit having an effective resonant length of one half of the selected wave length in the high television band) I first added a conventional, quarter wave, phase reversing stub between each two adjacent units of each set. With this arrangement, the two sets of collinear units were rotated about their longitudinal axes to dispose the stubs at various angles to the vertical and to dispose the stubs of one at various angles with respect to the stubs of the other (no reflectors being employed). One such arrangement is diagrammatically illustrated in Fig. 10 where the stubs Su of the upper set hang downwardly in a vertical plane and the stubs S1 of t e lower set pr j ct. upwardly in the same.

plane. A conductor'ci was' connected between the center units of the two sets on one side of the central break therein, and a parallel conductor G2 was connected between the center units of the two sets on the opposite side of the central breaktherein. The terminal ends T1 and T2 of a twoocnductcr radio frequency transmission line were connected to the mid-points of the conductors C1 and C2. i r

With the general arrangement shown in Fig. 10, the gain of the antenna over the entire high and low television bands reached its maximum at about 195 megacycles anddropped off sharply to less than half the maximumat 1'70 inegacycles and to less than two-thirds the maximum'at 229 megacycles. In the low band, the gain reached a maximum of about li3% of the high band maximum at 65 megacycles and dropped oil sharply to about 50% of the low band. maximum at 50 megacycles and to less than 50% of the low band maximum at 917 megacyclesl The characteristics of this "antenna as regard the impedance match of the antenna to the line (standing wave ratio) corresponds closely to the gain characteristics, as should be expected. In the high band, this ratio was about 1.25 at about 190 megacycles, but rose sharply to about 4 at 220 megacycles and to about 4.7 at 170 mega'cycles. In the low band, this ratio was a minimum of about 2.3 at about 65 megacyeles and rose sharply to about 3.9 at 90 megacycles and to about 4.2 at 50 megacycles. Since the required condition for high gain broad band performance is a standing wave ratio near unity over the entire useful band, it is apparent that this antenna showed no particularly unusual broad band characteristics, though the gain at the optimum frequencies was very good. i

Rotation of the two sets of collinear units to vary the angles of the planes of the stubs to the vertical had essentially no effect on the standing wave ratio or gain of the antenna over any part of the high and low bands. When the planes of the stubs were horizontal, the radiation pattern of the antenna in a horizontal plane, measured with horizontally polarized waves, exhibited slight lobes at the 90 position, but this effect was small and varied only slightly with frequency.

Thus, while the tWo sets of vertically stacked collinear units with phase reversing stubs could be connected in parallel by conductors C1 and C2 to obtain greater gain, the combination was still responsive only to a very narrow range of frequencies, regardless of the orientation of the two sets. The addition of reflectors produced the expected effects of further increasing the gain and making the combination more highly directional, but nothing more. i

After considerable experimentation, I finally electrically connected the stubs of one set to the respectively alignedstubs of the other set, as diagrammatically illustrated in Fig. 11. Upon testing the performance of this arrangement, startling broad-banding efiects were obtained. The gain over the high television band reached substantially the same maximum as thearrangement of Fig. at about 190 megacycles, but it fell oil slowly not over 5% up to 220 megacycles and down to 170 megacycles. In the low band, the gain reached a maximum at about 65 megacycles, which was about greater gain than was obtained in this band with the arrangement in Fig.

10, and the gain fell oil slowly only about. up to 90 megacycles and only about 20% down to ,50 megacycles. The standing Wave ratio curves were similar to the gain curves when plotted against frequency. In the high band, this ratio varied between the optimum figure of 1.25 at 190 megacycles to a maximum of only about 1.5 at 220 megacycle's and 1.6 at 170 megacycles. In the low band, the optimum ratio Was about 1.75 at 65 megacycles and rose only to about 2.8 at 90 megacycles and 2.1 at 50 megacycles. This remarkable uniformity of gain at the high level indicated by the standing wave ratio over the entire high band, and the excellent characteristics in the low band with the same antenna, far excel the performance characteristics of any antenna with which I am familiar. For an easier comparison of the improvement obtained with the antenna of Fig. 11 over the antenna of Fig. 10, reference may be made to the following tabulation of the figures given in the foregoing discussion with approximate intermediate values added:

Standing Wave Gain, Per Cent Frequency Ratio Maxima (Megacycles) Fig. 10 Fig. 11 Fig. 10 Fig. 11

Per cent Per cent 50 4. 2 2. l 50 60 2. 7 l. 75 93 65 2. 3 1. 75 100 70 2. 7 1. 8 98 96 80 2- S 2. 2 78 82 90 3. 9 2. 6 47 75 4. 7 1. 6 40 95 2. 0 1. 4 82 98 1. 25 1. 25 100 100 200 1. 5 1. 3 90 99 210 2. 7 1. 4 78 97. 5 220 4. 0 l. 5 65 96 I am unable to explain, by any satisfactory analysis of the arrangement shown in Fig. 11, why it has the outstanding performance characteristics described above. Connecting the stubs back-to-back, however, is obviously largely re-' sponsible for such performance characteristics, which far exceed anything achieved heretofore to the best or my knowledge.

Upon translating this electrical arrangement into a physical form suitable for commercial production, I first constructed each pair of back-to back stubs Se and S1 of three conductor elements C3,C4, and C5 (Fig. 11) so that the assembled aerial resembled a ladder with the stub conductors C3 and C4 and the center set of interconnecting conductors C1 and C2 forming the rungs and holding the two sets of collinear units in fixed, spaced, parallel relation. When preassembled on the cross arms 13 and l 4, this structure is so bulky as to make packaging and shipping costs prohibitive. If shipped disassembled, the assembly time required at the point of installation is excessive compared to other aerials of simpler con struction, but inferior performance, which have been in wide commercial use. To overcome these commercial objections to my new aerial arrangement, 1 have devised a collapsible physical emhodiment of the electrical elements which can be compactly packaged for shipment and quickly ex tended and mounted at the point of installation.

Referring again. to Figs. 1 and 2 and also to Figs. 5, 6, 8, and 9, collapsibility of the unit shown therein is achieved by constructing each pair of back-to-back stubs (such as Su and S1 in. Fig. 11) of five pivotally connected conduct-or elements in:- stead of three conductor elements. Thus, each upper stub includes a pair of parallel, vertical conductors 46a and 41a, and each lower stub includes a pair of identical, parallel, vertical con.-

ductors 46b and 41b; and a common, short conductor 48 is pivotally connected at one end to both the upper and lower aligned conductors 46a and 46b, and at its opposite end to'both the upper and lower aligned conductors 47a and 4112. These pivotal connections may conveniently be made by forming loops in the ends of the conductors to be joined and simply inserting a machine screw through the loops, applying a nut loosely thereon, and mutilating the threads on the portion of the screw that projects beyond the nut to prevent its accidental removal.

The upper ends of the conductors 45a and 41a are also pivotally connected, respectively, to the adjacent ends of the associated upper collinear units 42 and M, or 53 and ll, and to the intervening insulator 29, as shown in Figs. and 6. Similarly, the lower ends of the conductors 46b and 471) are pivotally connected, respectively, to the adjacent ends of the associated lower collinear units 42 and M, or is and M, and to the intervening insulator 29. The machine screws which may suitably be employed to form these pivotal connections, such as the screws 32, preferably have the vertical cenductors applied after the nuts 33 have been applied and tightened, and additional nuts 5! are then loosely applied. Again, the assembly may be held together against accidental removal of the nuts 5i from the machine screws by mutilating the threads of the portions of the screws that project beyond the nuts.

Similarly, the conductors C1 and C2, to which the terminal ends T1 and T2 of the transmission line are connected in Fig. 11, are respectively replaced in Fig. 1 by an identical pair of vertically aligned conductors 52a and 52b and by another identical pair of vertically aligned conductors 53a. and 53b. The upper ends of the conductors 52a and 53a are pivotally connected, re spectively, to the adjacent ends of the sections 4m and Mb, of the central collinear unit 4!.

The lower ends of the conductors 52b and 53b are pivotally connected, respectively, to the adjacent ends of the sections Ala and Mb of the lower collinear unit 4!, These pivotal connections may be made in the same manner shown in Figs. 5 and 6.

The adjacent ends of the upper and lower conductors 52a and 521) are pivotally connected to each other and to one end of a short insulator 54, as by a suitable machine screw and nut; and the adjacent ends of the upper and lower conductors 53a and 531) are similarly connected to the opposite end of the short insulator 54. The terminal ends 56 and 51 of a two-conductor radio frequency transmission line, such as a conventional twin-lead line, are respectively connected to these pairs of upper and lower conductors, the connections conveniently being made by means of the same machine screws and nuts employed on the short insulator 54.

With this structural arrangement of the pairs of back-to-back stubs and the pair of conductors to which the transmission line leads are attached, three parallel motion linkages are provided for connecting the upper set of collinear units to the lower set of collinear units, as diagrammatically illustrated in Fig. 9. The fully extended positions of the various elements of the structure are indicated in Fig. 9 in dot-dash lines, and the partially collapsed positions of the elements of the structure are shown in solid lines. The collapsing action is also illustrated, in part, by Fig. 8, showing the partially collapsed parallel motion linkage formed by the conductors 52a, 52b, 53a

and 53b to which the leads of the transmission lines are connected.

This collapsible structure permits the entire aerial unit to be completely assembled in the factory with the machine screws and nuts forming the various pivotal connections loosely assembled, as described above. By moving the upper, relatively rigid frame of collinear units and cross-arm [3 toward the lower frame of collinear units and cross-arm M, the completely assembled structure may be collapsed into a compact unit, little thicker in its vertical dimension than the combined vertical height of the two brackets employed for mounting the aerial unit on the mast I 2. If it is desired to collapse the structure further to form a still flatter package, these brackets may be left 01f the assembly at the factory and packaged loosely therewith.

When the collapsed unit is removed from a package or carton at the location where it is to be installed, the structure may readily be pulled out to its fully extended condition and the nuts and machine screws forming the pivotal connections may be quickly tightened by means of a screw-driver and suitable wrench or pliers. The

resulting structure, when mounted on the mast l2 in the manner described above, is sufficiently strong and rigid to withstand winds of gale force.

The antenna assembly of this invention is adapted-to be duplicated, to the extent desired to obtain still further gain, by stacking one such assembly above another on the same mast and connecting them to the transmission line in parallel in a well known manner.

While the features of the invention responsible for high gain, broad band performance have been illustrated as applied to sets of collinear units comprising three units each, they are applicable to arrangements having any desired larger number of collinear units per set. An odd plurality of collinear units per set is preferred, because of the natural impedance match of the antenna to the transmission line when the line is connected through transverse conductors to a center unit of each set at a central break therein. However, with suitable matching of the impedance of the antenna to that of the line, by adjusting in a well known manner the impedance of the transverse conductors to which the line leads are attached, excellent characteristics can also be obtained with four, six, eight, etc. collinear units per set. With an even number of units per set, the line leads are, of course, connected to transverse conductors respectively joining adjacent ends of the center-most units in one set to adjacent ends of corresponding units in the other set.

The structural features of the invention which render the fully assembled aerial unit collapsible are obviously applicable to numerous other forms of aerials. Accordingly, the scope of the invention is to be construed as limited to aerials employing spaced sets of collinear units only as re quired by the terms of the appended claims.

For convenience, in this specification and in the appended claims, the terms antenna and antenna system have been employed to designate the entire energy receiving or transmitting apparatus that is normally connected to the antenna terminals of a transmitter or receiver, and the term aerial has been employed to designate only the energy radiating or intercepting members and their physical supporting structure, excluding the transmission line.

From the foregoing description of my inven-' tion, it will be appreciated that I have provided a high gain antenna system having remarkable broad band characteristics. It will also be appreciated that the system has been embodied in a physicalform which may be preassembled in the factory, packaged, and shipped in a collapsed condition and quickly extended and made rigid at the place of installation for convenient mounting on a single, vertical mast of any desired type. It will also be appreciated that these operational results have been accomplished with greater than usual economy of materals.

Having described my invention, I claim:

1. In an antenna system, the combination with a two-conductor radio frequency transmission line of a pair of substantially identical, parallel sets of separated collinear units of substantially equal resonant lengths, there being at least three separated collinear units per set and said sets being spaced apart in transverse alignment, a first pair of conductors extending transversely with respect to said sets in electrically separated relation and connecting symmetrically spaced points of one unit of one set to corresponding points on the corresponding unit of the other set, an even plurality of additional pairs of conductors extending transversely with respect to said sets and symmetrically arranged on opposite sides of said first pair, each of said additional pairs of transverse conductors connecting adjacent separated ends of units in one set to corresponding ends of units in the other set, the conductors of said transmission line being respectively connected to the mid-points of said first pair of conductors, and short longitudinally extending conductors respectively connecting the transverse conductors of each of said additonal pairs together at their 'midpoints.

2 In an antenna system, the combination with a two-conductor radio frequency transmission line of a pair of spaced parallel sets of separated collinear units of substantially equal resonant lengths, there being an odd plurality of at least three such units per set, parallel transverse conductors connecting the adjacent ends of adjacent units in one set to the respectively corresponding ends of the units in the other set to provide parallel pairs of said transverse conductors, the transverse conductors of each of said pairs being electrically connected at their midepoints, an additional pair of parallel transverse conductors respectively connecting symmetrically spaced points on one center unit to like points on the other center unit, and the conductors of said transmission line being respectively connected to the mid-points of said additional pair of transverse conductors.

3. In an antenna system, the combination with a two-conductor radio frequency transmission line of a pair of spaced parallel sets of separated collinear units of substantially equal resonant lengths, there being an odd plurality of at least three such units per set and the spacing of the units of each set being small with respect to the unit lengths, parallel transversely extending conductors connecting the adjacent ends of adjacent units in one set to the respectively corresponding ends of the units in the other set to provide parallel pairs of transverse conductors, the transverse conductors of each of said pairs being electrically connected at their mid-points, the center unit of each set being broken at its mid-point for connection to said transmission line, an additional pair of parallel transverse conductors respectively connecting points on one center unit 10 to like points on the other center unit at each side of the breaks therein, and the conductors of said transmission line being respectively connected to the mid-points of said additional pair of transverse conductors.

4. In an antenna system, the combination with a two-conductor radio frequency transmission line of a pair of spaced parallel sets of separated collinear units of substantially equal resonant lengths, there being an odd plurality of at least three such units per set, the spacing of the units of each set being small with respect to the unit lengths and the spacing of said sets being substantially equal to the unit lengths, parallel transversely extending conductors connecting the adjacent ends or adjacent units in one set to the respectively corresponding ends of the units in the other set to provide parallel pairs'of transverse conductors, short longitudinally extending conductors respectively connecting the transverse conductors of each of said pairs at their midpoints, an additional pair of parallel transverse conductors respectively connecting symmetrically spaced points on one center unit to like points oh the other center unit, and the conductors of said transmission line being respectively connected to the mid-points of said additional pair of transverse conductors.

5. In an antenna system, the combination with a two-conductor radio frequency transmission line of a pair of parallelsets of separated collinear units of substantially equal resonant lengths, said sets extending horizontally and being spaced apart in a vertical plane, there being an odd plurality of at least three such units per set, the spacing of the units in each set being small with respect to the unit lengths and the vertical spacing of said sets being substantially equal to the unit lengths, vertically extending conductors connecting the adjacent ends of adjacent units in one set to the respec-' tively corresponding ends of the units in the other set to provide pairs of closely spaced vertical conductors, short horizontal conductors respectively connecting the vertical conductors of each of said pairs at their mid-points, the center unit of each set being broken at its midpoint for connection to said transmission line, an additional pair of closely spaced vertical con ductors respectively connecting points on one center unit to like points on the other center unit at each side of the breaks therein, and the conductors of said transmission line being respectively connected to the mid-points of said additional pair of vertical conductors.

6. An antenna aerial comprising a pair of spaced parallel sets of collinear units, there being at least three separated collinear units or" equal resonant lengths per set, a first pair of conductors extending transversely with respect to said sets in electrically separated relation and connecting symmetrically spaced points on the center unit of one set to corresponding points on the center unit of the other set, at least two additional pairs of conductors extending transversely with respect to said sets and symmetrically arranged on opposite sides of said first pair, each of said additional pairs of transverse conductors connecting adjacent ends of separated units of one set to corresponding ends of separated units of the other set, the transverse condoctors of each of said additional pairs being electrically connected at their mid-points.

'7. An antenna aerial comprising a pair of' spaced parallel sets of separated collinear units,

there being at least three such units of substantially equal resonant lengths per set and the center unit being broken at its mid-point, a first pair of electrically separated parallel transverse conductors respectively connecting electrically separated points on the center unit on opposite sides of the break therein to corresponding electrically separated points on the center unit of the other set, a pair of transmission line terminals respectively located at the mid-points of said transverse conductors, at least two additional pairs of transverse conductors parallel to said first pair and symmetrically arranged on opposite sides of said first pair, each of said additional pairs of transverse conductors connecting connecting the adjacent ends of adjacent units in one set to the respectively corresponding ends of the units in the other set to provide parallel pairs of said transverse conductors, the transverse conductors of each of said pairs being electrically connected at their mid-points, the cen ter unit of each set being broken at its midpoint, an additional pair of parallel transverse conductors respectively connecting points on one center unit to like points on the other center unit at each side of the breaks therein, and terminals at the mid-points of said additional pair of transverse conductors for connection respectively to the leads of a two-conductor transmission line. a

9.1m antenna aerial comprising a pair of rigid, spaced, parallel rectilinear reflectors, a pairof parallel sets of collinear units composed of three units each, said sets of collinear units being respectively rigidly mounted on said rer'lectors in spaced, transversely aligned, parallel relationship with respect to each other and parallel to said reflectors, each plane defined by a reflector and the collinear units mounted thereon bein normal to the planes defined by said refiectors and by said collinear units respectively, all of said units being of substantially the same resonant length and the spacing of the units in each set being small with respect to the unit lengths, transversely extending conductors connecting the adjacent ends of adjacent units in one set to the respectively corresponding ends of the units in the other set to provide parallel pairs of said transverse conductors, the transverse conductors of each of said pairs being electrically connected at their mid-points, an additional pair of parallel transverse conductors respectively connecting symmetrically spaced points on one center unit to like points on the other center unit, and terminals at the midpoints of said additional pair of transverse conductors for connection respectively to the leads of a two-conductor transmission line.

10. An antenna aerial comprising a pair of rigid, spaced, parallel, rectilinear reflectors, brackets on said reflectors for mounting them horizontally on a vertical mast, a pair of sets of collinear units composed of three unitseach, said sets of collinear units being respectively rigidly mounted on said reflectors independently of said brackets in spaced, parallel, transversely aligned relationship with respect to each other and in spaced parallel relationship with respect'to said reflectors, each plane defined by a reflector and the collinear units mounted thereon being normal to the planes defined by said reflectors and by said collinear units respectively, all of said units being of substantially the same resonant length and the spacing of the units in each set being small with respect to the unit lengths, transversely extending conductors connecting the adjacent ends of adjacent units in one set to the respectively corresponding ends of the units in the other set to provide parallel pairs of said transverse conductors, the transverse conductors of each of said pairs being electrically connected at their mid-points, the center unit of each set being broken at its mid-point, an additional pair of parallel transverse conductors respectively connecting points on one center unit to like points on the other center unit at each side of the breaks therein, and terminals at the midpoints of said additional pair of transverse conductors for connection respectively to the leads of a two-conductor transmission line.

LEWIS H. FINNEBURGH, JR.

7 REFERENCES CITED The following references are of record in the file of this patent:

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